The aqueous solubilities of guaiacol (2-methoxyphenol) and seven chlorinated guaiacols are reported at 25 degrees C, and for five of these over a temperature range from 5 to 45 degrees C, from which the enthalpies of solution are deduced. It is shown that the solubilities are well correlated with molar volume and that chlorinated phenols and guaiacols follow similar solubility-molar volume and vapor pressure-molar volume relationships. This does not, however, apply to 1-octanol-water partition coefficients. It is concluded that the equilibrium partitioning of the chlorinated and methoxylated phenols is more complex than has been generally assumed and that an improved understanding is required of the fundamental determinants of partitioning among water, air, octanol, and lipid phases of this important class of environmental contaminants.